<?php
        //get logged in username
        $username = $_SESSION['username'];
        //connect to the database
        include ('connect.php');
        $query = ("SELECT * FROM staff WHERE username ='$username'");
            $result = mysqli_query($connect, $query);
                //fetch associative array
                while($row = mysqli_fetch_assoc($result)){
                    //get staff id
                    $id = $row['staff_id'];
                    //Join staff and class tables o foreign key class_year and select all data based on the staff id
                    $sql = "SELECT * FROM staff INNER JOIN class ON staff.class_year = class.class_year WHERE staff_id = '$id' ";
                    $result = mysqli_query($connect, $sql);
                    if ($result->num_rows > 0) {
                            ?>
                            <select name = "class_year">
                                <option selected="selected" disabled='disabled'>Please Select</option>
                                <?php
                                while($row1 = mysqli_fetch_array($result)) {
                                    ?>
                                    <option><?php echo $row1['class_year'];?></option>
                                    <?php
                                }
                            }
                            ?>
                        </select>